1. Field of the Invention
The present invention generally concerns a golf club head. More particularly, the present invention relates to optimally positioning the center of gravity of a hollow-construction golf club head made of a metallic material such as titanium, titanium alloy, stainless steel or similar.
2. Description of the Prior Art
It can be said that the performance of a golf club head, namely, the ball distance traveled and traveling direction, greatly depends upon the position of the center of gravity and moment of inertia of the golf club head. Recently, there are many available types of golf club heads made of metallic materials having high specific strength, respectively, and each having an increased volume and reduced weight. In these situations, many proposals have been made to review and improve the shape and structure of the golf club heads in connection with the problems of the center of gravity position and the moment of inertia.
Generally, the geometry of the golf club head center of gravity includes parameters such as gravity height, depth and distance (a minimum distance of the center of gravity from the extension of the shaft axis), etc. Therefore, a metallic golf club head of the hollow-construction is designed with major consideration to such parameters of the center of gravity to optimally position the center of gravity for a player's skill and usage of the golf club.
Indeed, the conventional golf club heads manufactured based on the above proposals, for example, hollow-configuration large or "jumbo" heads made of such a metal having a high specific strength as titanium, for example, had implemented an increased inertia of moment about the center of gravity and also increased spins of a golf ball struck with such a golf club head, thereby allowing average skilled golfers to enjoy an easier swinging of the golf club and increased distance of ball flight. For these purposes, the golf club head was designed for the center of gravity to be lower and deeper in the head. The golf club with such a head will perform its designed function when used by an average skilled golf player who can swing the club head at a speed that is not so high. However, when a golf ball is struck with such a golf club by golfers having middle and upper grades of skill who can swing the club head at a higher speed and at a high ratio of meeting the sweet area of the head, too much back spin will be imparted to the golf ball more frequently when unnecessary, which is not any advantage for the skilled players.
Also, if the entire sole portion of the head is designed rather more thicker than the rest to have a low gravity, the vertical moment of inertia of the head about an axis passing through the head center of gravity and parallel to the ground will be unbalanced, so that striking a golf ball at an upper portion of the front face will possibly result in a direction of ball flight not intended or a high, weak ball not traveling a long distance. Also even if other than the sole portion is designed to be more lightweight by thinning of the wall, using a lighter material or otherwise, the head has to be balanced by distributing, to the sole portion, most of the corresponding weight thus reduced, thus the head cannot be designed to be larger.
Furthermore, it has been proposed to position only the center of gravity nearer to the front face of the golf club head. In this case, however, since no consideration is given to the gravity height, the center of gravity is positioned higher as it is placed nearer to the front face of the head. The golf club head thus designed will have characteristics suitable only for the highly skilled golf players including professional golfers.